Portable products using rechargeable batteries have their voltage regulated commonly by a linear regulator. Likewise, a charger applying a rate of charge to a battery typically has means of regulating the current to the battery. Regulating the energy provided to the load from a rechargeable battery and separately regulating the energy provided to a rechargeable battery is an inefficient system using a redundancy of circuitry. A need exists to eliminate this redundancy by supplying one circuit for both functions.
Battery packs for portable products are typically available in a variety of capacities and in a variety of battery cell chemistries. A battery charger generally cannot determine the charge capacity and battery cell chemistry inexpensively. U.S. Pat. No. 4,006,396 by Bogut discusses an inexpensive universal battery charging scheme which provides an electrical element within the battery pack having a characteristic related to a predetermined charging rate of the battery. The corresponding charger has a sensing circuit that recognizes the characteristic electrical element and thus provides the optimum charging rate for the corresponding battery capacity. This charging scheme as well as other common battery charging schemes requires that the charger sense the type of battery that is being charged. The sensing circuits within chargers increases the cost of the chargers and are typically limited in distinguishing between cell chemistries. Thus, a need exists for circuitry within a battery pack or system that would allow an optimum charging rate to the battery without external battery capacity and chemistry identification sensing.
The means for regulating charger current to a rechargeable battery is typically located within the charger. Likewise, a battery operated unit (such as a two-way radio) retains the means for regulating the energy from the battery to the battery operated unit. In both instances, the battery itself fails to retain the interfacing regulation circuitry. Typically, less efficient linear down regulators are used instead of the more efficient switching regulators in order to prevent electromagnetic interference (EMI). Although, switching regulators are more efficient, the shielding required within a radio or battery operated device sensitive to EMI would add greater expense, size, and complexity to the battery operated device. On the other hand, linear regulators create heat when functioning as current limiting devices. Thus, a need exists for circuitry within a battery pack that not only optimizes the charging rate to the battery, but also regulates energy to a load such as a battery operated device while overcoming the deficiencies of EMI and heat generation.